Inspection of bulk materials is a tedious task. In the food processing industry, for example, great care is taken to eliminate defective food articles from being passed on to the consumer. Detection of flaws or blemishes in small cut vegetable pieces is especially difficult due to the high number of small food articles being processed.
In the past, food articles were hand graded and sorted. This process is unsatisfactory due to human error and inconsistencies in human judgment. Vast improvements have been made to eliminate human error by implementing optical inspection systems. A very effective optical inspection system is disclosed in U.S. Pat. No. 4,581,632 granted in 1986 to the assignee of the present application. The system has capability of optically inspecting at volumes considerably higher than previously possible using manual visual techniques. In fact, the disclosed inspection system could operate at even higher capacity but for the slow feeding and transport mechanisms used to move the product past the inspection mechanisms.
Optical inspection is best effected when the product being inspected is relatively stable while being moved past the inspection station. Prior inspection apparatus have not effectively stabilized food products for inspection at high speed. Adequate article stabilization has been achieved only by the use of slow moving conveying and feed mechanisms.
U.S. Pat. No. 3,761,134 to Hurd discloses a decelerator mechanism for slowing the progress of articles on an air cushion conveyor. The apparatus includes three cushioned rollers mounted at radially oriented positions in relation to a central rotating shaft. The cushioned rollers rotate above the conveyor surface. The forward edges of articles passing along the conveyor will impact the rollers. The slower moving rollers apply a decelerating force, slowing the progress of the article or a grouping of similar articles riding on the air cushion. While effective for its intended purposes, such apparatus has not been found satisfactory in an optical inspection system where the articles must be stabilized in laterally spaced orientations across a moving support surface.
Various hold down and cushioning mechanisms are also known. Such apparatus is shown by U.S. Pat. Nos. 1,749,156; 4,279,338; 1,514,281; and 2,154,844. Such apparatus are useful to hold bulk articles in position on conveyor systems. However, such apparatus is not suited to the particular purpose of stabilizing individual articles in spaced relation on a surface in an article inspection system. The various hold down and cushioning apparatus will temporarily halt or adjust the velocity of articles but typically do not assure a maintained stationary relationship between the article and moving support surface once the articles leave engagement with the hold down mechanism.
Stabilization of articles in discrete, laterally spaced orientation for high speed inspection, has therefore remained a problem. So, where quality inspection is desired, conveying systems have been run at speeds below the capacity of the inspection apparatus in order to achieve the product stability required by the inspection apparatus.